On the way back from carving up the world at the Yalta conference in 1945, Franklin Roosevelt made an unexpected stop. On board the USS Quincy, moored in Egypt’s Great Bitter Lake, the president held a long meeting with Ibn Saud, the first Saudi monarch and father of the 45 sons (nobody seems to have bothered to count the daughters) who make the kingdom’s succession so operatic. Ibn Saud slaughtered a goat on the deck of the warship, sealing a pact that makes his kingdom America’s oldest continuous ally in the region. It is also the most troubling one.

On January 9th Raif Badawi, a blogger, received the first of his 1,000 lashes for taking Thomas Paine’s view of the “adulterous connection between church and state”. Mr Badawi has also been sentenced to a decade in prison. Three days later a woman accused of murder was dragged through the streets of Mecca and beheaded with a sword.

Though America disapproves of this sort of thing, it does not let it upset relations. Government delegations to the kingdom are usually lots of men in military uniform and one official from the State Department, whose job is to say that it would be nice if women could drive.

Scott Fitzgerald wrote that the ability to hold two opposing ideas in mind at the same time is the sign of a first-rate intelligence. Something similar applies in foreign policy. Ford Fraker, a former ambassador to Saudi Arabia, describes the alliance as “a long-term marriage founded on fundamental interests and principles”. Those interests have shifted a little over time. Now they could be summarised as oil, counter-terrorism and stability.

Like diamond earrings on an anniversary, weapons and money have been exchanged throughout as tokens of esteem. Less than a year after telling an audience in Cairo that America “must never alter or forget our principles”, Barack Obama performed a full Fitzgerald, signing off on one of the largest arms deals with the kingdom yet, an order now being fulfilled by American manufacturers.

Senator John McCain, just back from a trip to the kingdom, says that the country feels let down by America’s reluctance to punish Bashar Assad. “They had planes on the runway ready to go,” he says. “They learned it was not going to happen from watching CNN.” The Saudis, he says, are worried about expanding Iranian influence in the region–more so than they are about Islamic State (IS). This disagreement, and the recent hospitalisation of the 90-year-old king, makes it a good time to consider how America should treat the kingdom in future.

The high point of the relationship came during the presidency of Ronald Reagan, says Bilal Saab of the Atlantic Council, a think-tank. Memories of two Arab oil embargoes at a time of flat domestic oil production, as well as shared hostility to the Soviet Union, drew the countries close. There followed a blip after 9/11, when 15 of the 19 hijackers turned out to be Saudis. Al-Qaeda attacks in Saudi Arabia between 2003 and 2005 brought the countries closer together again. Though they may dent America’s idea of itself as a champion of liberty, government policy is that good relations are worth it. That may have been true in the Gipper’s day, but the argument is getting harder to make.

Oil is one reason. America may be the world’s biggest producer, but because consumption still exceeds what it pumps it must still shop on the world market. This does not make it dependent on Saudi Arabia, though. Oil is fungible: lousy relations with Russia, the second-biggest producer, do not threaten America’s economy. As the owner of the biggest reserves, which are also very cheap to extract, Saudi Arabia is the crucial swing producer. But America’s shale technology has put a ceiling on the oil price, and its economy is less oil-intensive than three decades ago.

Nor is the argument for keeping close for intelligence-sharing purposes as straightforward as it seems. Salafi Muslim terrorists, who draw much of their inspiration from Saudi imams, are a big threat to America. The pact between the House of Saud and the country’s clerics has long involved bankrolling Salafi imams to preach loyalty to the king; the money that sloshes through Salafi mosques undermines more moderate strains of Islam all around the world.

The black-robed fighters of IS rely on Saudi jurisprudence and books to impose their preferred version of Islamic law. Their fondness for public beheadings is one result of this. Intelligence co-operation may be valuable, but its main task is tracking threats that have been subsidised by the Saudis themselves.

That leaves the argument that the House of Saud must be supported because it is stable. The alternative could be much worse: the thought of something like IS controlling the world’s largest oil reserves is terrifying. Also, if America were to pull back from the Gulf, it is a fair bet that China would sooner or later replace it.

Some say that there is no alternative to the House of Saud. “This is a society that has the government they want,” says Ambassador Fraker. “They are comfortable with what they have.” If the regime is as secure as it seems, however, why should America abandon its basic values in the name of keeping it in place?

Free to scream

Strip these things away and what’s left is the arms sales. These at least have the virtue of being nakedly self-interested. Selling weapons is a big part of American diplomacy in the kingdom. A recent ambassador worked for Raytheon, the world’s biggest producer of guided missiles, before he was appointed. It is also popular in Congress: the defence business is adept at scattering production around as many districts as possible.

Yet this has a cost. Being a superpower means having relations with lots of unsavoury regimes, yet America need not be so eager to put principle aside when dealing with its old ally. “Failure to speak to the broader aspirations of ordinary people will only feed the suspicion that has festered for years that the United States pursues our interests at their expense,” as Mr Obama once put it. Between lashes, Mr Badawi no doubt agrees.